Misleading Graphs ( Quantitative Techniques and Methods )
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Misleading Graphs
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Misleading Graphs is the topic from the Quantitative Techniques and Methods
Transcript of Misleading Graphs ( Quantitative Techniques and Methods )
Misleading Graphs
A common saying
There are three types of lies• Lies•Damn Lies•Statistics
• When looking at a graph - always look at the scales used on both axis, the labels, and the size and shape of graph.
• Find out who ran the study, where did they get their data from, and what are they comparing.
• Look to see if they left anything out - did they take some points of data out of context?
Principles of Graphical Excellence• Well-Designed Presentation of Data that
Provides:– Substance– Statistics– Design
• Communicate Complex Ideas with Clarity, Precision and Efficiency
• Gives the Largest Number of Ideas in the Most Efficient Manner
• Almost Always Involves Several Dimensions• Telling the Truth about the Data
Errors in Presenting Data
• Using ‘Chart Junk’
• No Relative Basis in Comparing Data between Groups
• Compressing the Vertical Axis
• No Zero Point on the Vertical Axis
‘Chart Junk’
Good Presentation
1960: $1.00
1970: $1.60
1980: $3.10
1990: $3.80
Minimum Wage Minimum Wage
0
2
4
1960 1970 1980 1990
$
Bad Presentation
No Relative Basis
Good PresentationA’s received by
students.A’s received by
students.
Bad Presentation
0
200
300
FR SO JR SR
Freq.
10
30
FR SO JR SR
%
FR = Freshmen, SO = Sophomore, JR = Junior, SR = Senior
Compressing Vertical Axis
Good Presentation
Quarterly Sales Quarterly Sales
Bad Presentation
0
25
50
Q1 Q2 Q3 Q4
$
0
100
200
Q1 Q2 Q3 Q4
$
No Zero Point on Vertical Axis
Good Presentation
Monthly SalesMonthly Sales
Bad Presentation
0
39
42
45
J F M A M J
$
36
39
42
45
J F M A M J
$
Graphing the first six months of sales.
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Children Under 18 Who Own Cell Phones
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Food Votes
Pizza 972
Hot Dogs 987
Burgers 955
Instructions:
A survey has been taken to determine people's favoritie food. The results are shown in the table above.
Two graphs have been made for the same data. Which graph do you think is better? More fair? Why?
Graph 1
950
955
960
965
970
975
980
985
990
995
1000
Pizza Hot Dogs Burgers
Favorite Food
Num
ber o
f Vot
esGraph 2
0
100
200
300
400
500
600
700
800
900
1000
Pizza Hot Dogs Burgers
Favorite Food
Num
ber o
f Vot
es
